Timing tips

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Map63Vette

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So I recently swapped the old MSD Hemi 6 off my 5.7 and upgraded my Megasquirt setup to an MS3X to run full sequential and spark control in a single box. Generally speaking things are running pretty well, but I'm having some issues working out some reduced power over my old setup and a really bad shake at highway speed in 6th gear (0.5:1 overdrive with a 3.55 rear end in my case, around 1600 rpm).

To start with, I put the factory timing tables that have been posted online in as my base timing settings. I have a tableswitch set up to run the "closed loop/cruise" table normally, and then swap over to the "open loop/WOT" table when my TPS goes over 90%. Cruising around town and idling the car is awesome and a noticeable improvement over the old setup. However, full throttle hits even in first feel pretty lackluster to me. The old setup would blow the tires off or at least chirp them, but the new tuning just feels really lazy until maybe 5000 rpm when it picks up again. Trying to cruise 70 in 6th is near impossible as the car will just shake hard and have a hard time keeping the speed.

For reference, I'm running a 5.7 with an Inertia Motorsports SRT Max Plus cam with a little tighter LSA (I think it's something like 107 or 109), stock 6.1 exhaust springs, an Indy ModMan intake, TTI headers, all backed up by a Viper T56. I know the ModMan isn't a great intake and my system as a whole may not be super well matched, but I loved the sound of the cam in videos I'd seen and this is just where I am today.

I have a feeling I need more timing in both cases, but wanted to get some opinions and see if anyone else had a setup even remotely similar to mine. Looking at the stock WOT timing table there is a massive crater from ~3000-5000 rpm where the timing drops 5 degrees before working its way back up (picture below).

WOT Timing Curve.jpg


This seems to correspond to what I'm feeling in the seat of my pants, and I'm thinking maybe my cam and intake don't need the same kind of timing dip as the stock setup due to the different runner dynamics and cam timings. I'm planning to try flattening that out to see if it brings any life back. The high gear cruising problem I'm less sure about. I have a feeling it's a similar problem of not enough timing, but that one is a little harder for me to figure out. I'm running close to 80-85% load, but super low rpm. The factory table has me around 15-18 degrees of timing at this point while lean cruising at 14.7 AFR. I know lean cruise can take a lot more timing than full power, but I wouldn't have thought I'd be way off of factory numbers for this. Ideally I'd sit in the passenger seat and feed it timing a degree at a time while someone else is driving to see if it smooths out, but I haven't had a chance to try that yet. Looking for any ideas or datalogs people have done though to try to get a better idea of what is out there before I mess with timing too much.
 
Be very careful with "more timing." I ain't an expert on 3G hemis but I've read they don't need or want very much compared to older engines. Low 20's sometimes
 
Yeah, I'm definitely very aware of the low timing values on the modern hemis. For sure I'm not planning to go much over 20 for WOT, I think I'm just trying to figure out how soon to get there. Looking at some other maps it seems like they ramp to that kind of number pretty quick and just hold it through the rpm band.

Cruising is a tougher one. You can certainly run quite a bit higher timing in those conditions and really should when running on the leaner side of things. Just hard on my setup since I run really high load in high gear, but low RPM, so I tend to be in the top of the table. There's just less discussion out there about cruise timing.
 
What timing device are you running? crank trigger, cam trigger, timing wheel? Reading up on the opti-spark fiasco with the LT1 motors mentioned terrible low speed triggering.
 
I'm running the stock crank and cam sensors with the MS3X. Older engine, so 36-2+2 wheel or something like that based on what I read about the trigger wheel setup. Seems to be a nice clean signal (Hall sensors).

One other thing I've been thinking about is my dwell setting. The DIYAutoTune article I used to set things up recommended 2 ms to start with, but I'm wondering if maybe I need to bump that just a bit. Going to see if I can scope a coil to determine when it saturates if possible so I can know for sure, but not holding my breath that my scope will work that well.

Found the EFISource timing map on here earlier as well, so thinking I may try to blend that with the map I have as I'm not that fond of the low RPM values, but the higher RPM and load stuff looks a little better.
 
What are the cam specs and
what is your steady-state cruise timing in top gear?
How does it cruise one gear down?

A long time ago I ran a cruise gear that got me 65=1600 in double overdrive, 85@2100.
One gear down for me was 65=2050
I ran an awful lot of cruise-timing with that; about 46* at 1600/ 50 at 2100. It couldda used more.
But
this was with an 11/1, alloy-headed 360LA/ 600VS cruiser-carb, adjusted pretty lean. Car did over 30 mpgs on that trip.
The cam was a 223/230/110 and was a lil big for 1600, but really liked 2100.
Engine had enough power to hit 106@3650 pounds/ 1320.
 
What numbers are most useful to you on the cam specs? I've got the cam card here. The short version is 267/275 intake/exhaust duration and 0.549/0.536 lift intake/exhaust. LSA is 110 as it turns out. It says 4 degrees of advance ground in. 106 intake centerline and 114 exhaust.

From my understanding it was about the biggest cam you can use with "stock" springs and pistons. It doesn't have much for vacuum and idles around 50-60% load (which is basically 50-60 kPa absolute pressure, where 103 kPa is WOT).

Cruise rpm in 6th is around 1600 at 70 mph, down in 5th I think it's more like 2000 or maybe 2200. It will cruise in 5th okay, though you might just feel a shake if you hit a big enough hill. It used to run just fine with the old MSD, and I'm trying to figure out how much advance it was running. Looks like it was maybe a hair over 20 at the same place in the map that mine is today, so I'm fairly sure that's my problem, but it's just tough since that's also right on the edge of "WOT" in a way, just at super low rpm. Though I wonder if I push the advance up I might be able to drop the throttle some and bring it more into line.

The more I look at the "factory" timing tables, the more skeptical I am that they can be taken at face value. I know some of the old Dodge computers had layer and layers of tables and modifiers, so the final actual number for something like injector time may have very little to do with the actual number in a table from the start. The factory values seem so different from anything like the stock MSD curve or the EFISource tables, so I'm beginning to think maybe I should try one of those tables first. The MSD table tops out at around 18 degrees of timing WOT, which feels about right for my 87 octane setup. I'll have to transfer the curves on it to table format and see how it compares across the full range.
 
There is an engine masters episode where they discuss wot timing requirements on a gen 3 hemi and the myth that they don’t need or want timing. I’ll see if I can find it. The stock curve is very conservative and the “dip” you see is likely to compensate for knock at the torque peak with the stock cam. Your values will be different because of your cam and intake change. 5 degrees is a lot of timing to pull at peak tq but not it’s not uncommon to see a dip in the map. You just need more tuning time. You’ll get there.
 
Engine masters episode 79 in season 5. what they found is 27-28 degrees of total timing was optimal, with eagle heads and a cam swap. That was with a Holley terminator ecu.
 
Just saw the 87 octane you mentioned. I would not run the timing I posted above on that gas. Just an FYI
 
What numbers are most useful to you on the cam specs? I've got the cam card here. The short version is 267/275 intake/exhaust duration and 0.549/0.536 lift intake/exhaust. LSA is 110 as it turns out. It says 4 degrees of advance ground in. 106 intake centerline and 114 exhaust.

From my understanding it was about the biggest cam you can use with "stock" springs and pistons. It doesn't have much for vacuum and idles around 50-60% load (which is basically 50-60 kPa absolute pressure, where 103 kPa is WOT).

Refresh your screen.
I know nothing about those hemis.
Does that engine have VVT ?
My head is not getting sense of;
267/275/110, together with .549/.536 lift and
"It doesn't have much for vacuum"
Unless those are durations at some other than "normal" advertised lifts.

>At the usual .006/.008 tappet rise, that is a very conservative cam, and should be pulling a very large vacuum like 17 inches (guessing)
>But if that is at .050, then it is a very big cam, which would have a very low vacuum.
>So as it is, the numbers are meaningless to me. They need to have the accompanying qualifier.

In my street experience with iron wedge-heads on small-blocks, they all like about the same WOT power-timing, after 3600, in the range of 34 to at most 38 degrees. The only experience I have with alloy heads is my personal ride a 360LA, which is happy at ~32/34.
that said;
" Bucking", which is what I call what you are experiencing during very-low rpm cruising, is actually misfiring that is usually caused by running lean with insufficient timing. It seems to me that the air-molecules are too far apart, for the very few and far-apart, fuel-molecules to find them. So the fire starts but sputters out, therefore little to no effective pressure is made, and that piston now has to be carried by the others, costing the engine power, and you feel it as "bucking", especially if multiple cylinders are doing it.
So then, by moving down a gear, several things happen; you move up the fuel delivery curve therefore running less lean, and usually, the engine will have more timing up there, AND you get a lil more flywheel out of it. But more importantly, the higher rpm kills the reversion that happens with a very late intake valve closure, as the piston comes up and trys to ram it back up into the intake.
Or, I suppose, one or more of your injectors is not creating a fine-enough spray.
To run very lean, the molecules have to very tiny and well dispersed.
It may even be that they are being injected too late.
Or the overlap cycle is yanking a portion of them out into the headers, before the beginning of the intake cycle.
With a big cam, and low rpm, your O2 sensor may be as good as useless.
With headers, if there is any air infiltration whatsoever upstream of the O2 sensor, it will lie to you, and more importantly, it will lie to the computer. If the misfired fuel explodes in the header, two things will happen; that pipe will not scavenge on the next cycle because it destroys the vacuum cycle; and the exhaust in there now, is NOT representative of what should be in there.
This can also happen if the timing is too late, and the mixture has Not finished burning before the exhaust valve opens, and if it finds oxygen in the header.
If you are running exhaust logs, then this late-fire can ignite a misfired slug that is already in the log from another cylinder. On the overlap cycle, with a big cam, and at low rpm, this fire can zip over the top of the piston and try to get up into the intake.
These things are why I asked, "How does it cruise one gear down?"

This is how I do it, you can try it;
in Neutral/Park, slowly rev the engine up while watching the manifold vacuum. As the rpm climbs, the vacuum should steadily increase, as you are shutting the door to reversion, which is the fuel charge being bounced back up into the intake by the rising piston, before the late-closing intake valve actually closes.
Eventually the vacuum will hit a plateau, and then begin to decrease again; don't try to find that point if you haven't reached it be 3000rpm,lol. At the bottom of the plateau, or close to it, is where you want to cruise at. This is the lowest rpm that your engine has stopped sending just-inducted A/F charge back up into the intake, and all the fuel charge is going in the same direction and hopefully all of it is being trapped in the cylinder.
With a big street cam this may be as high as 2400rpm. With a small cam, like what a 318 has, this may be very close to idle!. With a typical street cam of 220 to 230 intake duration at .050, it will likely be around 1900, give or take a couple of hundred.
After this Fix the engine at whatever rpm created the highest vacuum. Now begin increasing the timing. As long as the rpm keeps on increasing, keep giving it more. This may take as much as 50/55 degrees. To speed his process up, jump the timing in steps of 3 or 4 degrees, until the gains are inconclusive. When that starts, back up 3 degrees. The number you get is, IS ideal, for that rpm and load.
After this, you gotta use logic to fill in the blanks.

Press refresh,
as I edited after first post, cuz I effed a few things up, lol.
 
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That is the "total" duration I guess. Duration at 0.050 is 218/226 intake/exhaust.

I just made a big comparison spreadsheet of the EFI Source table and the stock MSD table against the factory closed and open loop tables and interestingly enough the MSD one actually doesn't seem all that different from the stock table once it's converted into the same format. It does have its changes, but not as much as I would have thought looking at the curve initially. The EFI Source one definitely runs more top end timing and has no dip. The one I have has a very weird hole around typical idle values, but those are a bit too far down on the table for my idle. I'm not really sure I like the hole anyway, so I just put together a table that's a blend of the stock one at the lower loads and the EFI Source one at the upper range. I pulled some timing out in the high load/high rpm section where I have my AFR set to run rich for max power to try to start safer. The max it hits is right near 19, but is closer to 18 through the 3000-6000 range, which is similar to what the MSD curve was. That one had a dip at the end that carried all the way through to redline that I'm sure was probably a safety thing.

If I had the time and money I'd just rent a dyno for the day and run through the whole table and make it easy for myself. Use the dyno to load things up and just sit at every cell and dial up timing until the torque drops off, then back it off a few degrees and call it done. I may yet consider doing that someday, but need to find a place that would let me sit in the car and run it and the dyno to some degree. Most places don't seem to like that idea as much.
 
I have never tuned an EFI car, and am only familiar with carbs,
And there are several FABO members that considerably wiser than me on these matters.
But
I offer you this:
I cheat.
I have a stick-onto-the-window, accelerometer, that has data-logging capabilities. Mine is a G-tech-Pro-SS. With it, you can do a test run at any load setting and over what ever rpm range you want. It plots acceleration over time. Then I go home and play it back, looking for anomalys.
I also have a dash-mounted, dial-back, timing box with a range of 15 degrees; so I can change the timing on the fly, from the driver's seat.
It shows up on the SS as faster or slower acceleration thru the speed or rpm window.
The two tools cost me less than $500, and have paid for themselves many
times over.
Oh yeah, I had to make a throttle-stop early on, for Part-Throttle runs, for repeatability.
 
What vehicle is this engine in? You talk about wot tuning and cruise timing and then mention 87 octane and blowing the tires off all in one paragraph. Is this a truck? A hot rod? A cruiser? What’s the goal here? And are you stuck on the low octane gas requirement?
 
Sorry another question. Are you datalogging knock at all in the MS?
 
That is the "total" duration I guess. Duration at 0.050 is 218/226 intake/exhaust.

I just made a big comparison spreadsheet of the EFI Source table and the stock MSD table against the factory closed and open loop tables and interestingly enough the MSD one actually doesn't seem all that different from the stock table once it's converted into the same format. It does have its changes, but not as much as I would have thought looking at the curve initially. The EFI Source one definitely runs more top end timing and has no dip. The one I have has a very weird hole around typical idle values, but those are a bit too far down on the table for my idle. I'm not really sure I like the hole anyway, so I just put together a table that's a blend of the stock one at the lower loads and the EFI Source one at the upper range. I pulled some timing out in the high load/high rpm section where I have my AFR set to run rich for max power to try to start safer. The max it hits is right near 19, but is closer to 18 through the 3000-6000 range, which is similar to what the MSD curve was. That one had a dip at the end that carried all the way through to redline that I'm sure was probably a safety thing.

If I had the time and money I'd just rent a dyno for the day and run through the whole table and make it easy for myself. Use the dyno to load things up and just sit at every cell and dial up timing until the torque drops off, then back it off a few degrees and call it done. I may yet consider doing that someday, but need to find a place that would let me sit in the car and run it and the dyno to some degree. Most places don't seem to like that idea as much.
Do you have a picture of your set up on the engine. Does this have injectors in the manifold runners?
 
I have never tuned an EFI car, and am only familiar with carbs,
And there are several FABO members that considerably wiser than me on these matters.
But
I offer you this:
I cheat.
I have a stick-onto-the-window, accelerometer, that has data-logging capabilities. Mine is a G-tech-Pro-SS. With it, you can do a test run at any load setting and over what ever rpm range you want. It plots acceleration over time. Then I go home and play it back, looking for anomalys.
I also have a dash-mounted, dial-back, timing box with a range of 15 degrees; so I can change the timing on the fly, from the driver's seat.
It shows up on the SS as faster or slower acceleration thru the speed or rpm window.
The two tools cost me less than $500, and have paid for themselves many
times over.
Oh yeah, I had to make a throttle-stop early on, for Part-Throttle runs, for repeatability.

I've actually got something like that. I have an old Beltronics GX2 or something like that. The trick is getting all the suspension settings dialed in for it to be accurate, though I guess for a back to back comparison that wouldn't really matter much. And by "suspension settings", I mean the accelerometer has values for pitch and roll per G that you put in so it can cancel out the gravity it measures as the car tilts. But again, as long as I don't change those settings I should be able to do back to back plots, even if the actual values aren't "correct".

What vehicle is this engine in? You talk about wot tuning and cruise timing and then mention 87 octane and blowing the tires off all in one paragraph. Is this a truck? A hot rod? A cruiser? What’s the goal here? And are you stuck on the low octane gas requirement?

Sorry, it's a 67 Dart street car basically. Stock suspension, just a modern drivetrain (2006 5.7 Hemi and a Viper T56). 8 3/4 rear end with a posi unit and 3.55 gears. Former setup was a dual computer affair with a standalone MSD running ignition and a Megasquirt running fuel. Ran well and had some good pull, though I'm fairly sure not fully tuned to the engine's ability. A hard hit in first gear at low rpm would light up street tires and chirp my DOT drag tires with that setup in that it just hit hard and fast, though it did feel like it ran out of breath fairly early. New setup is a Megsquirt 3X running both fuel and ignition, fully sequential. I thought I put a similar timing map in it compared to what was in my MSD, but the car just didn't respond the same and felt lazy everywhere. It would cruise around town and idle nicely, but the most noticeable issues were the lazy full throttle stabs and the high speed high gear cruising. I've always run the car on 87 octane. I'm not forced into it by any means as I have the freedom to tune to whatever I'd like to put in it and 89 or 91 is readily available to me, I just never really wanted or tried to push the envelope. I can actually run a switch to swap between tables if I really wanted to as another option, though I doubt there's a whole lot to gain between 87 and 91 compared to something like pump gas and race gas.

As for the knock, no, I don't have any sensing capability at the moment. The Megasquirt can't take them as direct inputs (and I'm kind of running out of inputs already anyway). I need a conditioner board to handle the factory sensors, and I just haven't really messed with them yet. I have thought about adding them in one of these days, but I also know if I have a good tune in it with a little room for error I shouldn't really need them. Always nice to know though, so I may still get around to it one of these days.

Do you have a picture of your set up on the engine. Does this have injectors in the manifold runners?

Here's about the best I could find on the internet. The injectors do point more or less at the back of the valves. They shoot maybe just a little more inboard than down, but it's still more or less at the valve, not a throttle body style injection setup.
25b52d4e85bd60748c3eb?rik=dcQ7fIJlT12qrw&riu=http%3a%2f%2fwwww.indyheads.com%2fimages%2f426.6.1a.jpg
 
Also, I made up my own blend of the EFI Source table mixed with the factory table and ended up with this:

Timing Table.jpg


It's already a world of difference on a full throttle hit or any quick throttle jab. Pulls much harder right off the hit and carries it better through the full rpm range. I think it probably still has more to give if I wanted to bump it a few more degrees, but I'm trying to keep it safe for now. Highway cruise is also better, though maybe still just a few degrees shy of where it wants to be. I can cruise in 6th at 65 now pretty cleanly and maybe 70 on flat ground without much shake. It's running closer to 70% load and right around 20 degrees in that scenario, which is up maybe 3-4 degrees from where it was earlier. Thinking about throwing another 2-3 degrees at it and trying again to see if that cleans up the last of the shake. Overall it feels much more like what I would have expected out of the engine. I know it's not a fire-breathing monster, but power to weight it's similar to a C5 Vette and should have some get up and go to it. Now it at least feels like it's trying.
 
I've actually got something like that. I have an old Beltronics GX2 or something like that. The trick is getting all the suspension settings dialed in for it to be accurate, though I guess for a back to back comparison that wouldn't really matter much. And by "suspension settings", I mean the accelerometer has values for pitch and roll per G that you put in so it can cancel out the gravity it measures as the car tilts. But again, as long as I don't change those settings I should be able to do back to back plots, even if the actual values aren't "correct".



Sorry, it's a 67 Dart street car basically. Stock suspension, just a modern drivetrain (2006 5.7 Hemi and a Viper T56). 8 3/4 rear end with a posi unit and 3.55 gears. Former setup was a dual computer affair with a standalone MSD running ignition and a Megasquirt running fuel. Ran well and had some good pull, though I'm fairly sure not fully tuned to the engine's ability. A hard hit in first gear at low rpm would light up street tires and chirp my DOT drag tires with that setup in that it just hit hard and fast, though it did feel like it ran out of breath fairly early. New setup is a Megsquirt 3X running both fuel and ignition, fully sequential. I thought I put a similar timing map in it compared to what was in my MSD, but the car just didn't respond the same and felt lazy everywhere. It would cruise around town and idle nicely, but the most noticeable issues were the lazy full throttle stabs and the high speed high gear cruising. I've always run the car on 87 octane. I'm not forced into it by any means as I have the freedom to tune to whatever I'd like to put in it and 89 or 91 is readily available to me, I just never really wanted or tried to push the envelope. I can actually run a switch to swap between tables if I really wanted to as another option, though I doubt there's a whole lot to gain between 87 and 91 compared to something like pump gas and race gas.

As for the knock, no, I don't have any sensing capability at the moment. The Megasquirt can't take them as direct inputs (and I'm kind of running out of inputs already anyway). I need a conditioner board to handle the factory sensors, and I just haven't really messed with them yet. I have thought about adding them in one of these days, but I also know if I have a good tune in it with a little room for error I shouldn't really need them. Always nice to know though, so I may still get around to it one of these days.



Here's about the best I could find on the internet. The injectors do point more or less at the back of the valves. They shoot maybe just a little more inboard than down, but it's still more or less at the valve, not a throttle body style injection setup.
View attachment 1715861866
Cool set up. I have only had 2 experiences with the mod man intake on a gen 3. One carburetor and one throttle body and both were bad. If that manifold was to work at all the set up that you have would be it's best chance.
Also we dynoed a 6.1 stroker with a carburetor and found 24 degrees to the sweet spot for max power using a msd hemi box and mopar performance intake. This was on 92 pump gas and I know we whistled it but I don't remember the compression ratio.
 
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Also, I made up my own blend of the EFI Source table mixed with the factory table and ended up with this:

View attachment 1715861867

It's already a world of difference on a full throttle hit or any quick throttle jab. Pulls much harder right off the hit and carries it better through the full rpm range. I think it probably still has more to give if I wanted to bump it a few more degrees, but I'm trying to keep it safe for now. Highway cruise is also better, though maybe still just a few degrees shy of where it wants to be. I can cruise in 6th at 65 now pretty cleanly and maybe 70 on flat ground without much shake. It's running closer to 70% load and right around 20 degrees in that scenario, which is up maybe 3-4 degrees from where it was earlier. Thinking about throwing another 2-3 degrees at it and trying again to see if that cleans up the last of the shake. Overall it feels much more like what I would have expected out of the engine. I know it's not a fire-breathing monster, but power to weight it's similar to a C5 Vette and should have some get up and go to it. Now it at least feels like it's trying.
What do the numbers represent in the left vertical column?
 
What do the numbers represent in the left vertical column?

More specifically to the Megasquirt it's "load". The best way to translate that is "percent manifold pressure relative to atmospheric". That effectively normalizes the table to operate in different altitudes. So 100% means the manifold pressure is the same as atmospheric pressure, or WOT. 50% would mean half of atmospheric pressure, or 0.5 bar/50 kPA/~15 inHg. Since atmospheric pressure is really close to 100 kPa (103 nominally), you can almost just read it as straight pressure/vacuum though.

Easiest way to interpret the table is left to right is increasing rpm and bottom to top is similar to throttle opening closed to open. So bottom left is throttle closed low rpm (idle) and top right is WOT redline. In my case idle is more like far left around the middle instead of the bottom, but same idea.
 
I must not be reading that chart right. It looks like it's showing less timing at higher vacuum?

Yeah, that trips a lot of people up. It's not actually vacuum on that axis, it's pressure (absolute pressure to be more specific).
 
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